20 abr 2004udine bootcamp1 first analysis results of the crab nebula and mrk421 m. lópez moya...
TRANSCRIPT
20 Abr 2004 Udine bootcamp 1
First Analysis Results of the Crab Nebula and Mrk421
M. López MoyaU.C.M.
1. Analysis chain
2. Mrk421• Camera rotation study• Light Curve
3. Crab Nebula
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Analysis chain (1)
• Calibration and Pedestal substraction– Used the standard calibration classes– P,C runs selected by hand: needed a method to
look autmotically for the closer P,C runs to a given D run.
– Pedestal runs seem to work fine, but many problems using calibration runs: many pixels look after calibration.
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• Image cleaning– Lvl1 = 3.0, Lvl2 = 2.5 (one ring)– We started to investigate the dependence of
cleaning cuts, but no conclusive results yet: just that 5:3 seems to work better for the Crab.
– Forseen insland analysis and moun rings rejection, specially to analysis at low energies.
Analysis chain (2)
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• Signal Extraction– We use: MExtractSignal2
• Hillas Paramter cuts– for the time being, only use SIZE, LENGTH,
WIDTH & DIST.– we used static cuts: no dependence with zenith
angle took into accout
Analysis chain (3)
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• Getting the telescope pointing postion– Poiting position stored only in CC reports at a
fixed frecuency– For having it in an event by event base, we
extrapolated it using the arrival time of the event.
Analysis chain (4)
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• Data Set 15 Feb.2004
Mrk 421 (1)
Type Runs # Events Duration [m]
ON
P
C
D
17457
17458
17206-17456 1.019.354 104
OFF D 17459-17543 401.362 50
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Mrk 421 (2)
• Hillas cuts:
SIZE > 2000
0.1 < LENGTH < 0.3
0.05 < WIDTH < 0.12
0.6 < DIST < 1.4
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Mrk 421 (3)
• Correcting the mispointing: The False Source Plot– We consider as source position, the position at the
maximum in the 2D alpha plot
• Fitting the Alpha Plot– Signal region < 10– Backg. region: between 30 - 90– Fit the Backg. region to a 2nd order polinomial. From it
extrapolate the bg. in the signal region– The significance is calculated according to LiMa
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• We get nearly 20 , but a relative broad alpha plot.
• The significance is high enough to split this day into subsamples. This allows:– Study camera rotation: is really the rotation
uniform?– Get the ligth curve for that day
Mrk 421 (4)
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• We divide the whole night (1:45 h) into 10
subsamples
• Now, we don´t apply the camera rotation algorithm.
Mrk 421 : Camera rotation (1)
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• For each of the subsamples, we get the source position and it corresponding alpha plot.
• From each alpha plot, we get the number of excess events, that we plot vs. Time, obtaining the light curve for that night.
Mrk 421: Light curve (1)
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• BUT, this light curve depends strongly on:– the binning criterium (binning in RunNumber,
RunTime,...)– the hillas cuts
• Also we check the time stamp
Mrk 421: Light curve (3)
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• Data Set 15 Feb.2004
Crab Nebula (1)
Runs Duration [m]
ON 16745-16767
16830-16980
17036-17123
84
OFF 16770-16877
16894-17030
17126-17190
33
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• So far, only analyzed the night: 15 Feb 2004.
• For Mrk 421 seems easy to get a nice signal, without using a detailed calibration or cut optimization. We get around 20 .
• According the light curve, although we see some variation, it is difficult for the time being to relay on it.
• Mrk 421 also quite useful to understand telescope behaviour.
• For the Crab the situation is more complex. Seems that different cuts should be used. We get only about 6 .
Conclusions